1. Field of the Invention
The present invention relates to an apparatus for generating hydrogen gas (gaseous hydrogen), and particularly to an apparatus for generating hydrogen gas which can be mounted in a vehicle such as an electric vehicle and can supply hydrogen gas to fuel cells mounted in the vehicle.
2. Description of the Related Art
Conventionally, an electric vehicle carries fuel cells as a power source for obtaining driving force of the vehicle and is loaded with hydrogen, as a fuel which is used to carry out power generation in the fuel cells, or with a crude fuel which is used to produce hydrogen. Hydrogen is loaded on the electric vehicle in the form of a cylinder (tank) filled with compressed hydrogen gas or in the form of a hydrogen-absorbing alloy or hydrogen-absorbing material into which hydrogen is absorbed. Further, an electric vehicle loaded with a crude fuel is loaded with a hydrocarbon crude fuel, such as methanol or gasoline, and includes a hydrogen generator for generating hydrogen-rich gas by steam reforming the crude fuel.
However, hydrogen storage density of the hydrogen-absorbing alloy or hydrogen-absorbing material is not sufficient for use in fuel cells of an electric vehicle, and it is very difficult to control storage and absorption of hydrogen. Compared with an electric vehicle loaded with hydrogen, an electric vehicle loaded with a crude fuel has the advantage of a longer travelling distance on one supply of fuel, and also has the advantage that the crude fuels such as hydrocarbons are easier to handle and is safer to transport than hydrogen gas.
Decahydronaphthalene (Decalin), which is a hydrocarbon, has a vapor pressure of approximately zero at ordinary temperatures (the boiling point is close to 200° C.) and is easy to handle. Accordingly, the possibility that decahydronaphthalene can be used as the above-described crude fuel has been foreseen.
As a dehydrogenation method for decahydronaphthalene, a method has been known in which decahydronaphthalene is irradiated with light in the presence of a transition metallic complex containing at least one kind of transition metal selected from cobalt, rhodium, iridium, iron, ruthenium, nickel and platinum, and thus hydrogen is removed from the decahydronaphthalene (see Japanese Patent Application Publication (JP-B) No. 3-9091). Further, a method has also been known in which decahydronaphthalene is irradiated with light in the presence of a rhodium complex of an organic phosphorous compound or in the presence of an organic phosphorous compound and a rhodium compound, to produce hydrogen from the decahydronaphthalene (see Japanese Patent Application Publication (JP-B) No. 5-18761).
However, when one of the above-described conventional hydrogen generating methods is applied to a hydrogen-utilizing device such as fuel cells of an electric vehicle, a reaction conversion ratio is low, and naphthalene, unreacted decahydronaphthalene and the like produced by the dehydrogenation, are included. Accordingly, there exists a problem that hydrogen partial pressure is low and the efficiency of the hydrogen-utilizing device deteriorates.